The twentieth century was marked by two world wars. François de Breteuil, music composer, entomologist and pacifist was mobilized twice. Breteuil was occupied in 1940, 1942 and 1944 and finally liberated by a unit of the U.S. Army by order of Commander Burgess. François and his wife, Martine de Breteuil, an actress, had one son, Henri François. Since 1976, Henri François and his wife Severine Decazes have breathed some new life into the family castle after a long period of inactivity.
The castle, gardens and park were classified as a historical monument on June 18, 1973. The renovation work was carried out under the authority of the chief architects of the Service of Historical Monuments of the Yvelines, Jean Claude Rochette, Bernard and Philippe Oudin Fonquernie with, in part, support from the Ministry of Culture and the Parks District (Agence des Espaces Verts de la Région Ile-de-France). In 1987, the Regional Natural Park of the High Valley of Chevreuse (Parc Naturel Régional de la Haute Vallée de Chevreuse) was created. The Castle of Breteuil is one of its greatest attractions. Combining relaxation and culture, the area welcomes all visitors ranging from the very young to seniors. At the turn of the new millennium, Breteuil Castle, an ancient location with a rich past, has found its place in today’s world.